Dark Room exhaust/negative pressure

[Spits]

So i am planning running a DarkRoom 240 x 240 x 200 with 2x 1000w hps in it. I was reading about negative pressure but i still have to get this clear from you guys just for that peace of mind.

I would like to have 1x 8inch extractor fan 980m3/h sucking the hot air from 2x daystar(sealed/glass/6inch) 1000w each without carbon filter just expelling the hot air throu the roof hopefully without smell!?

Next i was thinking of setting on top of the darkroom another 8 inch extractor fan 980m3/h with an 8 inch carbon to suck all the smell(24/7) but i don't know if this is enough to create the negative pressure on my darkroom to eliminate all the smell from 32 plants on 11L pots coco in flower? Now for intake i was thinking on a 5 inch 480m3/h but maybe this is too much!? i don't know...

Last question what size pots and for how long should i veg to use 11l in flower. Maybe veg for 3 weeks in 6l pots? and start flowering after it with 11l!? don't forget its coco.

Soory about the english but its not my native language. But is all this even doable!? or just a nice fantasy!!?

 

[FreezerBoy]

I would like to have 1x 8inch extractor fan 980m3/h sucking the hot air from 2x daystar(sealed/glass/6inch) 1000w each without carbon filter just expelling the hot air throu the roof hopefully without smell!?

You say air is going through the reflectors but, you don't say where the air originates. If it comes from inside the room, it will smell and need to be scrubbed. Unscrubbed, the air would need to come from outside the room, be ducted through the lamps and out, never touching the air inside the room.

 

[Mr. Bongjangles]

All you need to do to maintain negative pressure is have your exhaust outpace your intake.

You plan on using an 8'' fan at 900 something cfm for exhaust and a 5'' fan at 400 something cfm for intake, so I'd say your plan will definitely result in negative pressure. Sounds like the lights will be on their own fan, so just do what freezerboy says on that note. Be sure to check the seal on the hoods themselves.. You don't want them sucking in unfiltered air through cracks or weak spots in the seal. Prolly less an issue with newer hinged reflectors, but keep it in mind just in case.

As for the pot size, that will be a factor of veg time and plant count. You'll need to find a middle ground that works for you.

In my case, I only have about 200 watts in veg to keep my 1k tent full. The balance I've struck is 2 batches of 8 plants with 30 days veg each. I use 2 gallon pots in veg and transplant to 4 gallon pots in flower, basically the biggest pots I can fit considering my plant numbers.

I could use smaller pots and increase my watering frequency, but I find that the extra root space always results in a little extra yield, even if the ones in smaller pots never get uncomfortable or even close to rootbound. Coco costs so little compared to the value of the results, so yea, I really recommend the biggest pots you can fit based on the number of plants you intend to run.

Let everyone know what your veg setup is like, and perhaps someone with something similar can give you a more specific recommendation for plant count and veg time.

 

[Spits]

You say air is going through the reflectors but, you don't say where the air originates. If it comes from inside the room, it will smell and need to be scrubbed. Unscrubbed, the air would need to come from outside the room, be ducted through the lamps and out, never touching the air inside the room.

So from what i could understand i got 2 options freezer boy sucking the hot air from the reflectors(sealed) with a carbon filter or getting cold air from outside window to the reflectors without carbon filter. Whats more efficient? what temperatures would have to be outside to cool 2000w?

Hi Mr. Bongjangles! I like your veg setup 30 days in 2 gallons and still you don't get rootbound? and your flower chamber is about 16 plants in 4 gallons? are the plants spaced or close to each other?

Thank you both for helping!

 

[FreezerBoy]

The plant will stink up the air in the room. Any air removed from the room will transport the smell with it (pic 1) Any air exiting the room has to be scrubbed (pics 2-3) the scrubber must go at the end of the line. Which end is arbitrary.

Pulling air from outdoors means dealing with outdoor temps (pic 4) Summer air may provide little cooling, winter air may add condensation inside the line (not sure on that but I don't know if I'd want to play with it.) Pulling air from another room (pic 5) would keep the cooling air in the 65º-85º range. Low enough to cool and high enough to prevent condensation. Note both examples 4-5 would still require a separate scrubber system.

 

[Spits]

The plant will stink up the air in the room. Any air removed from the room will transport the smell with it (pic 1) Any air exiting the room has to be scrubbed (pics 2-3) the scrubber must go at the end of the line. Which end is arbitrary.

Pulling air from outdoors means dealing with outdoor temps (pic 4) Summer air may provide little cooling, winter air may add condensation inside the line (not sure on that but I don't know if I'd want to play with it.) Pulling air from another room (pic 5) would keep the cooling air in the 65º-85º range. Low enough to cool and high enough to prevent condensation. Note both examples 4-5 would still require a separate scrubber system.

The picture and the explanation are awesome freezerboy very easy to folow. So in the end of the day i would have to had 2 carbon filters but the grows I see here usually just have one is there something wrong with the design room=?

Thanks again for the help!

 

[FreezerBoy]

Ventilation provides two services. Cooling is one, air exchange is the other. Most people combine these into a single line (such as pics 2-3 above) You're splitting them into two separate lines. A cooling line never uses air inside the grow room so there's no need to scrub. However a cooling line provides no air exchange. The line that exchanges air from the grow room will stink like the grow room and needs to be scrubbed. Even though there are two lines, there's only one that needs scrubbing.

The only reason you'd need two scrubbers is if both hoods were individually set up as combined runs (Cooling and exchange in one line)

As long as air flows through the room as fast as it comes in, then the inside air pressure will be lower, or negative. It's why airplanes fly and baseballs curve. This is why most use passive intakes. It places the bottleneck outside the cab rather than inside which intake fans will do.



I can't help with coco but, I will say that all indoor lights suffer from some lack of penetration. Outdoors, buds at the top and bottom of a 20 foot plant get the same light. Indoors, 6 inches costs you half your light strength or more.



My 250 gives me colas in the 19" range but, I grow horizontally in a ScrOG so they're only 6" tall. A 1K could easily grow a plant too tall for it to truly cover. I'd keep veg time to a month or less until you've seen what happens.